Improve code quality and write tests

node_modules/codecov/lib/git.js

@@ -0,0 +1,15 @@
+var execSync = require('child_process').execSync
+
+module.exports = {
+  branch: function() {
+    return execSync('git rev-parse --abbrev-ref HEAD || hg branch')
+      .toString()
+      .trim()
+  },
+
+  head: function() {
+    return execSync("git log -1 --pretty=%H || hg id -i --debug | tr -d '+'")
+      .toString()
+      .trim()
+  },
+}